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<pre><span class="sourceLineNo">001</span><a name="line.1"></a>
<span class="sourceLineNo">002</span>/*<a name="line.2"></a>
<span class="sourceLineNo">003</span> * Copyright (C) 2014 Archie L. Cobbs. All rights reserved.<a name="line.3"></a>
<span class="sourceLineNo">004</span> *<a name="line.4"></a>
<span class="sourceLineNo">005</span> * $Id: KVStore.html 878 2015-04-17 01:32:03Z archie.cobbs $<a name="line.5"></a>
<span class="sourceLineNo">006</span> */<a name="line.6"></a>
<span class="sourceLineNo">007</span><a name="line.7"></a>
<span class="sourceLineNo">008</span>package org.jsimpledb.kv;<a name="line.8"></a>
<span class="sourceLineNo">009</span><a name="line.9"></a>
<span class="sourceLineNo">010</span>import java.util.Iterator;<a name="line.10"></a>
<span class="sourceLineNo">011</span><a name="line.11"></a>
<span class="sourceLineNo">012</span>/**<a name="line.12"></a>
<span class="sourceLineNo">013</span> * General API into a key/value store where the keys are sorted lexicographically as unsigned bytes.<a name="line.13"></a>
<span class="sourceLineNo">014</span> *<a name="line.14"></a>
<span class="sourceLineNo">015</span> * &lt;p&gt;<a name="line.15"></a>
<span class="sourceLineNo">016</span> * Implementations are not required to support accessing keys that start with {@code 0xff}.<a name="line.16"></a>
<span class="sourceLineNo">017</span> * &lt;/p&gt;<a name="line.17"></a>
<span class="sourceLineNo">018</span> *<a name="line.18"></a>
<span class="sourceLineNo">019</span> * &lt;p&gt;&lt;b&gt;Lock-free Counters&lt;/b&gt;&lt;/p&gt;<a name="line.19"></a>
<span class="sourceLineNo">020</span> *<a name="line.20"></a>
<span class="sourceLineNo">021</span> * &lt;p&gt;<a name="line.21"></a>
<span class="sourceLineNo">022</span> * Implementations are encouraged to include support for encoding a 64 bit counter in a key/value pair such that the counter<a name="line.22"></a>
<span class="sourceLineNo">023</span> * can be efficiently {@linkplain #adjustCounter adjusted} by concurrent transactions without conflict.<a name="line.23"></a>
<span class="sourceLineNo">024</span> * In practice this means no locking is required to increment or decrement the counter by some amount, as long as<a name="line.24"></a>
<span class="sourceLineNo">025</span> * it's not necessary to actually directly read or write the counter value in the same transaction.<a name="line.25"></a>
<span class="sourceLineNo">026</span> * Whether counter adjustments are actually lock-free is implementation dependent, however, the counter methods<a name="line.26"></a>
<span class="sourceLineNo">027</span> * {@link #encodeCounter encodeCounter()}, {@link #decodeCounter decodeCounter()}, and {@link #adjustCounter adjustCounter()}<a name="line.27"></a>
<span class="sourceLineNo">028</span> * must function correctly as specified in all cases.<a name="line.28"></a>
<span class="sourceLineNo">029</span> * &lt;/p&gt;<a name="line.29"></a>
<span class="sourceLineNo">030</span> *<a name="line.30"></a>
<span class="sourceLineNo">031</span> * &lt;p&gt;<a name="line.31"></a>
<span class="sourceLineNo">032</span> * How counters are encoded is specific to the implementation. Clients needing to read or write counter values directly<a name="line.32"></a>
<span class="sourceLineNo">033</span> * should use {@link #decodeCounter decodeCounter()} and {@link #encodeCounter encodeCounter()}, respectively.<a name="line.33"></a>
<span class="sourceLineNo">034</span> * Counters are removed using the normal methods (i.e., {@link #remove remove()} and {@link #removeRange removeRange()}).<a name="line.34"></a>
<span class="sourceLineNo">035</span> * &lt;/p&gt;<a name="line.35"></a>
<span class="sourceLineNo">036</span> */<a name="line.36"></a>
<span class="sourceLineNo">037</span>public interface KVStore {<a name="line.37"></a>
<span class="sourceLineNo">038</span><a name="line.38"></a>
<span class="sourceLineNo">039</span>    /**<a name="line.39"></a>
<span class="sourceLineNo">040</span>     * Get the value associated with the given key, if any.<a name="line.40"></a>
<span class="sourceLineNo">041</span>     *<a name="line.41"></a>
<span class="sourceLineNo">042</span>     * @param key key<a name="line.42"></a>
<span class="sourceLineNo">043</span>     * @return value associated with key, or null if not found<a name="line.43"></a>
<span class="sourceLineNo">044</span>     * @throws IllegalArgumentException if {@code key} starts with {@code 0xff} and such keys are not supported<a name="line.44"></a>
<span class="sourceLineNo">045</span>     * @throws StaleTransactionException if an underlying transaction is no longer usable<a name="line.45"></a>
<span class="sourceLineNo">046</span>     * @throws RetryTransactionException if an underlying transaction must be retried and is no longer usable<a name="line.46"></a>
<span class="sourceLineNo">047</span>     * @throws NullPointerException if {@code key} is null<a name="line.47"></a>
<span class="sourceLineNo">048</span>     */<a name="line.48"></a>
<span class="sourceLineNo">049</span>    byte[] get(byte[] key);<a name="line.49"></a>
<span class="sourceLineNo">050</span><a name="line.50"></a>
<span class="sourceLineNo">051</span>    /**<a name="line.51"></a>
<span class="sourceLineNo">052</span>     * Get the key/value pair having the smallest key greater than or equal to the given minimum, if any.<a name="line.52"></a>
<span class="sourceLineNo">053</span>     *<a name="line.53"></a>
<span class="sourceLineNo">054</span>     * &lt;p&gt;<a name="line.54"></a>
<span class="sourceLineNo">055</span>     * If keys starting with {@code 0xff} are not supported by this instance, and {@code minKey} starts with {@code 0xff},<a name="line.55"></a>
<span class="sourceLineNo">056</span>     * then this method returns null.<a name="line.56"></a>
<span class="sourceLineNo">057</span>     * &lt;/p&gt;<a name="line.57"></a>
<span class="sourceLineNo">058</span>     *<a name="line.58"></a>
<span class="sourceLineNo">059</span>     * @param minKey minimum key (inclusive), or null for no minimum (get the smallest key)<a name="line.59"></a>
<span class="sourceLineNo">060</span>     * @return smallest key/value pair with {@code key &gt;= minKey}, or null if none exists<a name="line.60"></a>
<span class="sourceLineNo">061</span>     * @throws StaleTransactionException if an underlying transaction is no longer usable<a name="line.61"></a>
<span class="sourceLineNo">062</span>     * @throws RetryTransactionException if an underlying transaction must be retried and is no longer usable<a name="line.62"></a>
<span class="sourceLineNo">063</span>     */<a name="line.63"></a>
<span class="sourceLineNo">064</span>    KVPair getAtLeast(byte[] minKey);<a name="line.64"></a>
<span class="sourceLineNo">065</span><a name="line.65"></a>
<span class="sourceLineNo">066</span>    /**<a name="line.66"></a>
<span class="sourceLineNo">067</span>     * Get the key/value pair having the largest key strictly less than the given maximum, if any.<a name="line.67"></a>
<span class="sourceLineNo">068</span>     *<a name="line.68"></a>
<span class="sourceLineNo">069</span>     * &lt;p&gt;<a name="line.69"></a>
<span class="sourceLineNo">070</span>     * If keys starting with {@code 0xff} are not supported by this instance, and {@code maxKey} starts with {@code 0xff},<a name="line.70"></a>
<span class="sourceLineNo">071</span>     * then this method behaves as if {@code maxKey} were null.<a name="line.71"></a>
<span class="sourceLineNo">072</span>     * &lt;/p&gt;<a name="line.72"></a>
<span class="sourceLineNo">073</span>     *<a name="line.73"></a>
<span class="sourceLineNo">074</span>     * @param maxKey maximum key (exclusive), or null for no maximum (get the largest key)<a name="line.74"></a>
<span class="sourceLineNo">075</span>     * @return largest key/value pair with {@code key &lt; maxKey}, or null if none exists<a name="line.75"></a>
<span class="sourceLineNo">076</span>     * @throws StaleTransactionException if an underlying transaction is no longer usable<a name="line.76"></a>
<span class="sourceLineNo">077</span>     * @throws RetryTransactionException if an underlying transaction must be retried and is no longer usable<a name="line.77"></a>
<span class="sourceLineNo">078</span>     */<a name="line.78"></a>
<span class="sourceLineNo">079</span>    KVPair getAtMost(byte[] maxKey);<a name="line.79"></a>
<span class="sourceLineNo">080</span><a name="line.80"></a>
<span class="sourceLineNo">081</span>    /**<a name="line.81"></a>
<span class="sourceLineNo">082</span>     * Iterate the key/value pairs in the specified range. The returned {@link Iterator}'s {@link Iterator#remove remove()}<a name="line.82"></a>
<span class="sourceLineNo">083</span>     * must be supported and should have the same effect as invoking {@link #remove remove()} on the corresponding key.<a name="line.83"></a>
<span class="sourceLineNo">084</span>     *<a name="line.84"></a>
<span class="sourceLineNo">085</span>     * &lt;p&gt;<a name="line.85"></a>
<span class="sourceLineNo">086</span>     * If keys starting with {@code 0xff} are not supported by this instance, and {@code minKey} starts with {@code 0xff},<a name="line.86"></a>
<span class="sourceLineNo">087</span>     * then this method returns an empty iteration.<a name="line.87"></a>
<span class="sourceLineNo">088</span>     * &lt;/p&gt;<a name="line.88"></a>
<span class="sourceLineNo">089</span>     *<a name="line.89"></a>
<span class="sourceLineNo">090</span>     * &lt;p&gt;<a name="line.90"></a>
<span class="sourceLineNo">091</span>     * If keys starting with {@code 0xff} are not supported by this instance, and {@code maxKey} starts with {@code 0xff},<a name="line.91"></a>
<span class="sourceLineNo">092</span>     * then this method behaves as if {@code maxKey} were null.<a name="line.92"></a>
<span class="sourceLineNo">093</span>     * &lt;/p&gt;<a name="line.93"></a>
<span class="sourceLineNo">094</span>     *<a name="line.94"></a>
<span class="sourceLineNo">095</span>     * &lt;p&gt;<a name="line.95"></a>
<span class="sourceLineNo">096</span>     * The returned {@link Iterator} must not throw {@link java.util.ConcurrentModificationException};<a name="line.96"></a>
<span class="sourceLineNo">097</span>     * however, whether or not a "live" {@link Iterator} reflects any modifications made after its creation is<a name="line.97"></a>
<span class="sourceLineNo">098</span>     * implementation dependent. Implementations that do make post-creation updates visible in the {@link Iterator},<a name="line.98"></a>
<span class="sourceLineNo">099</span>     * even if the update occurs after some delay, must preserve the order in which the modifications actually occurred.<a name="line.99"></a>
<span class="sourceLineNo">100</span>     * &lt;/p&gt;<a name="line.100"></a>
<span class="sourceLineNo">101</span>     *<a name="line.101"></a>
<span class="sourceLineNo">102</span>     * &lt;p&gt;<a name="line.102"></a>
<span class="sourceLineNo">103</span>     * The returned {@link Iterator} is not guaranteed to be thread safe.<a name="line.103"></a>
<span class="sourceLineNo">104</span>     * &lt;/p&gt;<a name="line.104"></a>
<span class="sourceLineNo">105</span>     *<a name="line.105"></a>
<span class="sourceLineNo">106</span>     * @param minKey minimum key (inclusive), or null for no minimum (start at the smallest key)<a name="line.106"></a>
<span class="sourceLineNo">107</span>     * @param maxKey maximum key (exclusive), or null for no maximum (end at the largest key)<a name="line.107"></a>
<span class="sourceLineNo">108</span>     * @param reverse true to return key/value pairs in reverse order (i.e., keys descending)<a name="line.108"></a>
<span class="sourceLineNo">109</span>     * @return iteration of key/value pairs in the range {@code minKey} (inclusive) to {@code maxKey} (exclusive)<a name="line.109"></a>
<span class="sourceLineNo">110</span>     * @throws IllegalArgumentException if {@code minKey &gt; maxKey}<a name="line.110"></a>
<span class="sourceLineNo">111</span>     * @throws StaleTransactionException if an underlying transaction is no longer usable<a name="line.111"></a>
<span class="sourceLineNo">112</span>     * @throws RetryTransactionException if an underlying transaction must be retried and is no longer usable<a name="line.112"></a>
<span class="sourceLineNo">113</span>     */<a name="line.113"></a>
<span class="sourceLineNo">114</span>    Iterator&lt;KVPair&gt; getRange(byte[] minKey, byte[] maxKey, boolean reverse);<a name="line.114"></a>
<span class="sourceLineNo">115</span><a name="line.115"></a>
<span class="sourceLineNo">116</span>    /**<a name="line.116"></a>
<span class="sourceLineNo">117</span>     * Set the value associated with the given key.<a name="line.117"></a>
<span class="sourceLineNo">118</span>     *<a name="line.118"></a>
<span class="sourceLineNo">119</span>     * @param key key<a name="line.119"></a>
<span class="sourceLineNo">120</span>     * @param value value<a name="line.120"></a>
<span class="sourceLineNo">121</span>     * @throws IllegalArgumentException if {@code key} starts with {@code 0xff} and such keys are not supported<a name="line.121"></a>
<span class="sourceLineNo">122</span>     * @throws StaleTransactionException if an underlying transaction is no longer usable<a name="line.122"></a>
<span class="sourceLineNo">123</span>     * @throws RetryTransactionException if an underlying transaction must be retried and is no longer usable<a name="line.123"></a>
<span class="sourceLineNo">124</span>     * @throws NullPointerException if {@code key} or {@code value} is null<a name="line.124"></a>
<span class="sourceLineNo">125</span>     */<a name="line.125"></a>
<span class="sourceLineNo">126</span>    void put(byte[] key, byte[] value);<a name="line.126"></a>
<span class="sourceLineNo">127</span><a name="line.127"></a>
<span class="sourceLineNo">128</span>    /**<a name="line.128"></a>
<span class="sourceLineNo">129</span>     * Remove the key/value pair with the given key, if it exists.<a name="line.129"></a>
<span class="sourceLineNo">130</span>     *<a name="line.130"></a>
<span class="sourceLineNo">131</span>     * @param key key<a name="line.131"></a>
<span class="sourceLineNo">132</span>     * @throws IllegalArgumentException if {@code key} starts with {@code 0xff} and such keys are not supported<a name="line.132"></a>
<span class="sourceLineNo">133</span>     * @throws StaleTransactionException if an underlying transaction is no longer usable<a name="line.133"></a>
<span class="sourceLineNo">134</span>     * @throws RetryTransactionException if an underlying transaction must be retried and is no longer usable<a name="line.134"></a>
<span class="sourceLineNo">135</span>     * @throws NullPointerException if {@code key} is null<a name="line.135"></a>
<span class="sourceLineNo">136</span>     */<a name="line.136"></a>
<span class="sourceLineNo">137</span>    void remove(byte[] key);<a name="line.137"></a>
<span class="sourceLineNo">138</span><a name="line.138"></a>
<span class="sourceLineNo">139</span>    /**<a name="line.139"></a>
<span class="sourceLineNo">140</span>     * Remove all key/value pairs whose keys are in a given range.<a name="line.140"></a>
<span class="sourceLineNo">141</span>     *<a name="line.141"></a>
<span class="sourceLineNo">142</span>     * &lt;p&gt;<a name="line.142"></a>
<span class="sourceLineNo">143</span>     * The {@code minKey} must be less than or equal to {@code maxKey}; if they equal (and not null)<a name="line.143"></a>
<span class="sourceLineNo">144</span>     * then nothing happens; if they are both null then all entries are deleted.<a name="line.144"></a>
<span class="sourceLineNo">145</span>     * &lt;/p&gt;<a name="line.145"></a>
<span class="sourceLineNo">146</span>     *<a name="line.146"></a>
<span class="sourceLineNo">147</span>     * &lt;p&gt;<a name="line.147"></a>
<span class="sourceLineNo">148</span>     * If keys starting with {@code 0xff} are not supported by this instance, then:<a name="line.148"></a>
<span class="sourceLineNo">149</span>     * &lt;ul&gt;<a name="line.149"></a>
<span class="sourceLineNo">150</span>     *  &lt;li&gt;If {@code minKey} starts with {@code 0xff}, then no change occurs&lt;/li&gt;<a name="line.150"></a>
<span class="sourceLineNo">151</span>     *  &lt;li&gt;If {@code maxKey} starts with {@code 0xff}, then this method behaves as if {@code maxKey} were null&lt;/li&gt;<a name="line.151"></a>
<span class="sourceLineNo">152</span>     * &lt;/ul&gt;<a name="line.152"></a>
<span class="sourceLineNo">153</span>     *<a name="line.153"></a>
<span class="sourceLineNo">154</span>     * @param minKey minimum key (inclusive), or null for no minimum<a name="line.154"></a>
<span class="sourceLineNo">155</span>     * @param maxKey maximum key (exclusive), or null for no maximum<a name="line.155"></a>
<span class="sourceLineNo">156</span>     * @throws IllegalArgumentException if {@code minKey &gt; maxKey}<a name="line.156"></a>
<span class="sourceLineNo">157</span>     * @throws StaleTransactionException if an underlying transaction is no longer usable<a name="line.157"></a>
<span class="sourceLineNo">158</span>     * @throws RetryTransactionException if an underlying transaction must be retried and is no longer usable<a name="line.158"></a>
<span class="sourceLineNo">159</span>     */<a name="line.159"></a>
<span class="sourceLineNo">160</span>    void removeRange(byte[] minKey, byte[] maxKey);<a name="line.160"></a>
<span class="sourceLineNo">161</span><a name="line.161"></a>
<span class="sourceLineNo">162</span>    /**<a name="line.162"></a>
<span class="sourceLineNo">163</span>     * Encode a counter value into a {@code byte[]} value suitable for use with {@link #decodeCounter decodeCounter()}<a name="line.163"></a>
<span class="sourceLineNo">164</span>     * and/or {@link #adjustCounter adjustCounter()}.<a name="line.164"></a>
<span class="sourceLineNo">165</span>     *<a name="line.165"></a>
<span class="sourceLineNo">166</span>     * @param value desired counter value<a name="line.166"></a>
<span class="sourceLineNo">167</span>     * @return encoded counter value<a name="line.167"></a>
<span class="sourceLineNo">168</span>     * @throws StaleTransactionException if an underlying transaction is no longer usable<a name="line.168"></a>
<span class="sourceLineNo">169</span>     * @throws RetryTransactionException if an underlying transaction must be retried and is no longer usable<a name="line.169"></a>
<span class="sourceLineNo">170</span>     */<a name="line.170"></a>
<span class="sourceLineNo">171</span>    byte[] encodeCounter(long value);<a name="line.171"></a>
<span class="sourceLineNo">172</span><a name="line.172"></a>
<span class="sourceLineNo">173</span>    /**<a name="line.173"></a>
<span class="sourceLineNo">174</span>     * Decode a counter value previously encoded by {@link #encodeCounter encodeCounter()}.<a name="line.174"></a>
<span class="sourceLineNo">175</span>     *<a name="line.175"></a>
<span class="sourceLineNo">176</span>     * @param value encoded counter value<a name="line.176"></a>
<span class="sourceLineNo">177</span>     * @return decoded counter value<a name="line.177"></a>
<span class="sourceLineNo">178</span>     * @throws IllegalArgumentException if {@code value} is not a valid counter value<a name="line.178"></a>
<span class="sourceLineNo">179</span>     * @throws StaleTransactionException if an underlying transaction is no longer usable<a name="line.179"></a>
<span class="sourceLineNo">180</span>     * @throws RetryTransactionException if an underlying transaction must be retried and is no longer usable<a name="line.180"></a>
<span class="sourceLineNo">181</span>     * @throws NullPointerException if {@code value} is null<a name="line.181"></a>
<span class="sourceLineNo">182</span>     */<a name="line.182"></a>
<span class="sourceLineNo">183</span>    long decodeCounter(byte[] value);<a name="line.183"></a>
<span class="sourceLineNo">184</span><a name="line.184"></a>
<span class="sourceLineNo">185</span>    /**<a name="line.185"></a>
<span class="sourceLineNo">186</span>     * Adjust the counter at the given key by the given amount.<a name="line.186"></a>
<span class="sourceLineNo">187</span>     *<a name="line.187"></a>
<span class="sourceLineNo">188</span>     * &lt;p&gt;<a name="line.188"></a>
<span class="sourceLineNo">189</span>     * Ideally this operation should behave in a lock-free manner, so that concurrent transactions can invoke it without<a name="line.189"></a>
<span class="sourceLineNo">190</span>     * conflict. However, when lock-free behavior occurs (if at all) depends on the implementation.<a name="line.190"></a>
<span class="sourceLineNo">191</span>     * &lt;/p&gt;<a name="line.191"></a>
<span class="sourceLineNo">192</span>     *<a name="line.192"></a>
<span class="sourceLineNo">193</span>     * &lt;p&gt;<a name="line.193"></a>
<span class="sourceLineNo">194</span>     * If there is no value associated with {@code key}, or {@code key}'s value is not a valid counter encoding as<a name="line.194"></a>
<span class="sourceLineNo">195</span>     * would be acceptable to {@link #decodeCounter decodeCounter()}, then how this operation affects {@code key}'s<a name="line.195"></a>
<span class="sourceLineNo">196</span>     * value is undefined.<a name="line.196"></a>
<span class="sourceLineNo">197</span>     * &lt;/p&gt;<a name="line.197"></a>
<span class="sourceLineNo">198</span>     *<a name="line.198"></a>
<span class="sourceLineNo">199</span>     * @param key key<a name="line.199"></a>
<span class="sourceLineNo">200</span>     * @param amount amount to adjust counter value by<a name="line.200"></a>
<span class="sourceLineNo">201</span>     * @throws StaleTransactionException if an underlying transaction is no longer usable<a name="line.201"></a>
<span class="sourceLineNo">202</span>     * @throws RetryTransactionException if an underlying transaction must be retried and is no longer usable<a name="line.202"></a>
<span class="sourceLineNo">203</span>     * @throws NullPointerException if {@code key} is null<a name="line.203"></a>
<span class="sourceLineNo">204</span>     */<a name="line.204"></a>
<span class="sourceLineNo">205</span>    void adjustCounter(byte[] key, long amount);<a name="line.205"></a>
<span class="sourceLineNo">206</span>}<a name="line.206"></a>
<span class="sourceLineNo">207</span><a name="line.207"></a>




























































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